nVidia has been doing an OK job of releasing development kits for Tegra hardware, although sometimes they are a bit pricey for non-professionals.
But why not just use an iOS or Android phone or tablet? I know it's not as sexy as using something that calls itself a dev kit, but things have moved so fast it's easy to lose site of the fact that a cheap cellphone is now potentially a great brain for a robotics or other miscellaneous electronics project. Maybe packaging freedom is reduced because you don't have the bare board to wire into the enclosure of your choice, but these things are getting so tiny the form factor is easy to integrate into other projects, at least for prototyping. IO is a bit trickier, as you can't just wire stuff to a peripheral header on your phone, but there are products like BeagleBone and depending on the product you may be able to get access to a serial interface for communication between a phone and custom hardware.
Beyond consumer hardware, there are products like BeagleBoard, PandaBoard, Raspberry Pi and many professional OMAP and Tegra SO-DIMM SoC development kits that are roughly on par with mainstream phone hardware. There's a ton of stuff out there if you look, times are great for a hobbyist but sometimes you just have to wrap your head around the fact that you don't have to use something that has "developer" written all over it and a big price premium to get stuff done.
I gotta love the continued roll outs of multi-core graphics and general processing devices! I wonder if there is a plan for providing this device in a small demo board form factor for development efforts? I am thinking that this would make a great building block (graphics, processing power, wireless connectivity) for students working on college projects.
Awesome! 6X graphics improvement!! Now everyone can have retina display! I wonder how imagination's rogue GPU will stack up against this. In the last few rounds they totally destroyed Tegra 2/3 line.
BTW Watch out Intel!